Two of the victims suffered life-threatening injuries. One of the nine was a boy, 5, KBOI-TV, Boise, reported.
The driver of the vehicle, a man, was not injured and not identified.
"All of a sudden, out of nowhere, a white car, going very fast, came, and I just saw bodies flying. It was just awful," said Dee Cazier, whose daughter Amanda Olsen was among those injured.
Officials said the injured, some of whom were related, were taken to three local hospitals.
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